1. Field of the Invention
The disclosure relates to a medium winder and a medium unwinding method using the medium winder.
2. Description of Related Art
Heretofore, paper winders have been provided as medium winders for printers capable of printing on long paper from a web as a roll medium. Paper from a web that is printed and ejected from such a printer is wound by a paper winder as a medium winder.
In such a type of paper winder, the paper printed and ejected from the printer is wound around a winding roller. The paper winder includes a dancer roller. The dancer roller is moved up and down along a guide in accordance with an amount of sag generated in the paper so as to absorb the difference between the paper winding velocity in the paper winder and the paper conveyance velocity in the printer.
In the above-described printer, it is necessary to warm up a printing section at the start of the printing or cool down the printing section at the end of the printing. During the warming-up and cooling-down processes, unprinted paper is wastefully ejected from the printer and is wound around the winding roller. In order not to waste paper, the printer rotates the paper feed roller and the conveyance roller in reverse directions after the warming-up and cooling-down of the printing section so as to unwind the paper which is once wound around the winding roller in the paper winder.
In the process of unwinding the paper, the dancer roller also functions to absorb the difference between the paper unwinding velocity in the paper winder and the paper reverse conveyance velocity in the printer.
In the process of unwinding paper, the position of the dancer roller is detected in the paper winder. When the dancer roller reaches the upper end of the guide, a driving motor to rotate the winding roller, that is, a winding roller driving motor, is driven in the reverse direction to rotate the winding roller in reverse for unwinding the paper. When the dancer roller reaches the lower end of the guide, the winding roller driving motor is halted to stop the rotation of the winding roller, thus terminating the unwinding of paper (see Japanese Patent Application Publication No. S63-51261, for example).